Power-split transmissions of the type concerned have a continuously variable power branch, which can be made for example as a hydrostatic power branch or an electric power branch, and a mechanical power branch, which are summed together by means of a totalizing gear system. In addition, power-split transmissions of this type have at least two driving ranges which can be engaged by means of clutches and within which the drive output rotational speed of the power-split transmission can be varied continuously.
DE 102006055724A1 discloses a hydrostatic-mechanical power-split transmission of this type, in which the shift from a first driving range to a second driving range takes place with synchronous rotational speed, in order to achieve good shift quality without shift jerks. During the shift from one driving range to the other driving range, the transmission ratio in the continuously variable power branch is kept constant, so that the synchronous point remains unchanged during the shift.